1. Field
The present disclosure relates to a motor which can be used in an appliance and its operation control method. More specifically, the disclosure relates to a self magnetizing motor, and a method of controlling and operating such a motor.
2. Background
In general, an induction motor is operated based on the principle that when a current flows in a wire within a magnetic field, power is generated from the wire according to Flemming's left-hand rule. In case where a rotation magnetic field is formed, and an induction current is generated in conductive bars installed within a rotor according to an electromagnetic induction law (Faraday's Law), the conductive bar receives a particular type of force according to the Flemming's left-hand rule and such force is converted into a rotary force.
In the case of an induction motor, when a rotational speed of the rotor reaches a synchronous speed, which is the rotational speed of the rotation magnetic field, an induction current is no longer generated from the conductive bars installed within the rotor. Thus, as the rotational speed of the rotor approaches the rotational speed of the rotation magnetic field, the rotational force exerted upon the rotor gradually decreases. However, in a typical induction motor, the rotational speed of the rotor never reaches the “synchronous” speed of the rotation magnetic field.
The rotational speed of the magnetic field is given by the equation rpm=(120) (frequency)/number of poles. Thus, when an AC current of 60 Hz (i.e., a typical AC frequency) is applied to a 2-pole induction motor, the synchronous speed is 3,600 rpm. However, in case of a typical induction motor, the actual rotational speed of the rotor is about 3000 rpm, which is smaller than 3,600 rpm. The difference between the synchronous speed and the actual speed is typically referred to as “slip.” In addition the rotor rotating at a lower speed, the slip represents an efficiency loss.